An X-ray computed tomography apparatus has an X-ray detector which detects X-rays and outputs digital data (raw data) in accordance with an intensity of the detected X-rays. The X-ray detector includes a data acquisition system (DAS) having a detector element array of a plurality of detector elements for detecting X-rays and a plurality of DAS elements for converting output signals from the plurality of detector elements into raw data.
Due to recent technological innovations, imaging with reduced X-ray dosages is being conducted more frequently. Usually, the dynamic range of the DAS is between 218 and 220; however, there are more and more instances of imaging with X-ray conditions of less than 210. In such a low dosage region, the performance advantages and disadvantages of the DAS such as circuitry noise, linearity of the X-ray detector, aging drift, temperature drift, and crosstalk, etc., cause image artifacts.
The plurality of detector elements and the plurality of DAS elements are respectively connected on a one-to-one basis. Accordingly, if there is a variation in performance among the plurality of detector elements and DAS elements, the variation causes image artifacts. Furthermore, the number of detector elements and DAS elements are increasing year by year, and the increase of the number of detector elements leads to a higher rate of X-ray detector failure. Since the failure rate of DAS elements is higher than that of detector elements, image artifacts due to the variation in performance among the DAS elements tend to increase, as the number of elements increases.